Vacuum dehydration of corn



Patented June 25, 1946 uNi'rao STATES PATENT oFFica '1 VACUUM DEHYDBATION 0F CORN Robert M. Schai'iner, Chicago, 111., assignor to The Gnardite Corporatlonya corporation of Illinote No'Drawing. Application'june 21, 1944, Serial No. 541,468

Thi invention relates to the vacuum dehydration of corn.

Corn dehydratedby conventional methods has a tendency to darken in'color on storage 'and the dehydrated product is frequently tough in texture and poor in flavor. It has been found that the vacuum dehydration herein described produces a greatly improved dehydrated material which has good flavor and texture on rehydration and the ability to reconstitute itself to a weight'at least 80% of that of the original material. e

Before drying, the corn is bl anched. The customary manner of blanching is in steam or hot water and, while these may be employed, the

vacuum blanching method herein described reduces the amount of handling, eliminates contact of the blanched corn with air, reduces the amount of corn milk losses, and improves the product.

In processing the material, the corn is husked, washed on the cob, cut by hand or by machine,

3 Claims. (Cl. 99-20 4) complished by reducing the pressure to /2 inch of mercury absolute. I

The corn is then dried in an atmosphere of superheated steam at low pressure, without ex- Dosing it to the air. This may be done either in the same chamber or in another chamber to which the corn i transferred .without breaking the vacuum.

and the kernels then loaded on screen bottom trays at densities ofabout 1.0 to 1.5 lbs. per square foot. The trays are then placed in a vacuum chamber and a vacuum drawn to reduce the pressure to approximately /2 inch of mercury. Steam is then admitted to the chamber to increase the pressure and raise the temperature of the corn from approximately 170 F. to 210 F., thepressure being from. 12 inches absolute to 28 inches absolute. The time required for blanching varies'with the temperature and 10 minutes is quite satisfactory at 180 F.

to 200 F. Slightly longer times are desirable below 180 F. but it is not necessary to reduce the time at the higher ranges. time of minutes at 200? I". gave a good product.

After blanching, the chamber is again evacuated which 0001; the product. This evacuation is preferably carried on to reduce the temperature to the neighborhood of F., this being ac- A satisfactory apparatus and method for handling the blanching is illustrated in Baer application 524,177, filed February 28,

.1944, and Heineman application 520,773, filed February 2, 1944.

The bulk of the drying energy is supplied through intense radiant heat supplied from steam coils surrounding the product and close to it. In the figures herein given, the coils were 2/4-inch external diameter pipes arranged 4 inch apart in horizontal banks above and below the trays with the nearest point of the coil 3 stant temperature which may be diilerent from that in the other banks.

The corn is dried to a moisture content not higher than 8% in a time of from '10 to min- For example, a

9 2w 1"., followed by a 90-minute exposure to autes. In a typical cycle the radiant energy source is first heated to 298 F. andthe corn exposed to that heat for 30 minutes, followed by a 20-minute exposure to a source maintained at source'maintained at 228 F. Radiant energy source temperatures, however, have been varied from 350 1". to F., the higher temperature always being at the beginning of the process.

The dehydration ratio reierred to in the table is the result obtained by dividing the raw weight of the corn by its dehydrated weight.

The rehydration ratio in the above table refers to the result obtained by dividing the rehydration weight by the dehydrated weight. The rehydrated weight is taken after boiling the dehydrated com for 30 minutes in water without previous soaking.

The reconstitution percentage is the rehydration ratio divided by the dehydration ratio which is the same thing as dividing the rehydrated weight by the raw weight.

' Batches 8, 9 and 10 were a more mature corn than the other batches. It will be noted that in all cases the corn was a fresh com and not the customary dried corn of commerce.

The foregoing detailed description has been iven for cleamess of understanding only, and no go unnecessary limitations should be understood therefrom.

What I claim as new and desire tosecure by Letters Patent is: I

1. The method of drying fresh corn which comprises removing the corn from the cob. spreading on trays, substantially removing air therefrom. blanching the corn in an atmosphere oisaturated The rollowin' 3 table gives example or corn:

" [Operatingvaouumpressunfiiaohu] TeltNo.

1 2 a 4 a o 1 s v 10 Variety Tendergoid Golden cross bantam Processed,hrs.aiter 48: 2%---" l 4 1K"... 18 21%. 24K. harvesting.

Originalt moisture, per 76.2...- 70.2 79.9.... 77.0.-.. 76.6.-.. 70.0... 70.0... 70.0.

oen Finalmoisture,percent. 7.0 7.2..." 70....- 5.4........ 7.2....- 6.1.-..- 0.5..... 7.4.. 5.5.. 70. Color Good,bet- Fain... Good Fair, dark- Good... Good... Good..- ExoeLdai-klxyeeeilmost Excel. darkow. er

and0 Flavor BO. taste... Good. Texture d Good o. Dehydration ratio.- .16 am--- 8.00. Rehydration ratio 3.20 2.75-. 2.58. Reoonstitution..-. 867...--. 90.8.......-.. 88.0. Pretreatment (other None None... None... None... 0 liters B01 gas None th usking and y! 000 min. 5" cutting aHS vac. Inading...lbs.lsq.it...- l.00....-.. l.00.,..- 1.06.... 1.04.....-. 1.04...- 1.09.-..'1.00...- 1.06.. 1.00... 1.06. Machine bianch ternperature ..F.- 185-194..-. 181 186-. 181-191.... 219-210- mo-.. 200-210. 200 :05 200. Time ..!ninuies.. 10.. 10..." 10 In 10 10 10. 10 10. Dryingcycle: P M P M P M P M P 'M P M P M P M P M r M P-steam coil [11) 30 60 30 60 30 60 30 60 30 60 30 00 30 30 50 I0 M, poun s/sq. 30 .20 5 140 8 150 6 140 10 20 10 20 6 150 10 10 6 160 8 160 in. Mminutes.......- 5 5 6 100 6 140, 170 180 170 I 150 180 im steam for about 10 minutes at a temperature of approximately 170-210 R, reducing the pressure, and then drying the blanched corn in an atmosphere of superheated steam while subject to intense radiant energy at low absolute presnot greaterthan 8% in the corn. 45 2. The method as set forth in claim 1, in which the corn is dried for 30 minutes while receiving radiant energy from a source maintained at approximately 298 F. and approximately 3 inches away from the corn, then for 20 minutes from a source similarly distant and maintained at approximately 2'14? F., and then for 90 minutes from a source similarly distant and maintained at approximately 228" F.

3. The method as set iorth in claim 1, in which the corn is loaded in the dryer at approximately 1.0 to 1.5 lbs. per square foot.

ROBERT- M. SCI-IAFFNER. 

